Abstract: When the pipeline structure in the space vehicle is subjected to the random vibration load, the fatigue damage will be accumulated in the welding part, and the normal flight of the space vehicle will be in danger. This paper analyzes the dynamic strength of a pipeline structure with welded joints in the space vehicle. Firstly, the finite element model of the pipeline structure is established, and the accuracy of the model is verified by the computational modal analysis and the experimental modal analysis. In view of the scattering nature of the material fatigue characteristics, the P-S-N curve of the welding material and the expression of the fatigue damage are obtained. Then, the structural stress method is used to analyze the fatigue damage of the complex pipeline welded structure, and the median fatigue life of the weak link is determined to be 5.23×10⁴ s. Furthermore, the relationship between the fatigue life and the reliability of the welded parts of the pipeline structure is obtained by the probability analysis method. The calculation results can provide a support for the reliability improvement of the pipeline structures and the reliability design of the whole structure.